1. Field of the Invention
This invention relates to remote disconnection and short-circuiting of a pair of conductors such as those used in telephone or other communications lines.
2. Description of the Prior Art
One of the most common types of fault in telephone lines is the appearance of resistive paths between legs of a pair to earth, or from one conductor of a pair to another. The resistance of such faults may vary from zero ohms to a megohm or more. The most common technique for locating such faults is to use a Varley bridge type fault locator which requires a short-circuit strap to be placed at one end of the suspect pair.
Usually the following fault location procedure is followed. A telephone technician places an audio-frequency oscillator on the pair at one end and then proceeds to the other end of the line. The technician then identifies the pair using a very high gas receiver which converts a received signal to an audio output. By searching through the cabling at the remote end of the line, the technician is able to locate the correct pair by looking for the conductors carrying the loudest signal and detecting the null, or area of no signal, in the gap midway between the conductors of the pair. This detection confirms and positively identifies the pair.
Varley fault location is only able to proceed when the oscillator end of the line is strapped, that is, short-circuited. At present, such an operation requires the technician to travel to the other end of the line, connect a strap to the line, and then travel back to the remote end, where the pair identification has taken place. He then connects the Varley fault locator and proceeds with the location of the fault.
Clearly, this manner of pair identification for fault location is inefficient and costly. The same disadvantages exist in present methods for the installation of telephones or other communications equipment.
In such a situation, the telephone pair is connected to a functioning telephone exchange, and thus has typically, 50V between the legs or conductors of the pair. The telephone installer connects an oscillator to the pair at the exchange, or at an intermediate point between the exchange and the subscriber's premises, and then proceeds to the cable joint nearest to the premises to locate the particular pair to which the telephone or other apparatus is to be connected.
Having located the pair, the installer must connect the telephone and undertake dial and ringback tests. Such tests are only able to be undertaken if the oscillator is firstly removed from the exchange end of--or intermediate point in--the line. This requires the installer to travel to the exchange or intermediate point to disconnect the oscillator from the pair. The installer then returns to the subscriber's premises, connects the telephone or other apparatus and is then able to call the exchange and ask for ringback tests to confirm that the line is operational.
As with fault location, the present installation procedure involves the technician in travel which is time-consuming and, as a result, costly. In some circumstances, when a technician at the non-exchange end of a line has access to a telephone operating on another line, or to radio communications equipment, he may be able to instruct a second technician at the exchange to perform certain functions at the exchange end of the line in question. However, such access is not usually available, and the use of a second technician would also be costly. Of course, many unmanned exchanges are now used, and if such an exchange were involved, or an intermediate pillar, such a second technician could in any event not be readily utilized.